Building polynitrogen clusters with metal–metal multiple bonds

Abstract

Metal–metal multiple bonds based polynitrogen complex clusters may become a class of high-energy, insensitive and green primary explosives. Five complexes containing chromium (Cr≡Cr), molybdenum (Mo≡Mo), tungsten (W≡W), technetium (Tc≡Tc) and rhenium (Re≡Re) metal multiple bonds with pentazole ligands were theoretically built. The metal–metal multiple bonds, metal-pentazole coordination bonds, molecular static and dynamic polarizability were investigated with density functional theory M06-L/LanL2DZ, The Wiberg bond order sequence of metal–metal is Mo–Mo > Cr–Cr > W–W > Re–Re > Tc–Tc Bidentate coordination bonds were formed between each metal–metal edge and two pentazole ligands, which strengthen the coordination bonds, and Wiberg bond order sequence of metal-pentazole is Re–N > W–N > Tc–N > Mo–N > Cr–N. The gaseous and solid phase formation enthalpies, enthalpies of sublimation and theoretical density of five complexes were predicted. As candidates for primary explosives, their detonation heats were calculated and the descending order is Re4(N5)8 > W4(N5)8 > Tc4(N5)8 > Mo4(N5)8 > Cr4(N5)8. M4N40 clusters may be a class of promising green primary explosives.